Some physical quantity measuring devices include an inner case for housing a battery or the like, an outer case for housing the inner case, and a base fixed to the outer case. For such physical quantity measuring devices, the inner case should desirably be fixed to the outer case. For instance, when a battery is housed in the inner case, a circumferential rotation of the inner case relative to the outer case can cause an accidental breakage of a wire connecting the battery to a detector outside the inner case. The inner case thus needs to be fixed to the outer case.
A typical example of the physical quantity measuring devices including the inner and outer cases is a transmitter including a stainless cylindrical outer plate, an aluminum chassis housed in the outer plate, and a neck attached to the outer plate and the chassis (Patent Literature 1: JP 5716028 B2).
In the typical example of Patent Literature 1, the neck is welded to the outer plate and screwed to the chassis.
In another typical example, a fixture is pressed inward to bring an elastic lock piece into engagement, thereby movably fixing an optical unit in a case (Patent Literature 2: JP 2006-012746 A).
In the typical example of Patent Literature 1, the outer plate, the chassis and the neck of which respectively correspond to the outer case, the inner case and the base, the inner case is fixed to the outer case by welding the neck to the outer plate and screwing the neck to the chassis. Such a structure for fixing the inner case to the outer case is complicated.
In the typical example of Patent Literature 2, the structure for fixing the optical unit to the case is merely disclosed, but preventing the rotation of the inner case relative to the outer case is not taken into consideration.